Community Manager for Focus Home Interactive.
Could you try these steps of us?
I think that he can try to :
- Die against the boss
- Exit the sewers
- When you are outside on the beach, quit the game
- Turn off his Xbox One, by pressing the power button until the "X" is completely turned off.
- Reboot the console
- Launch the game
- Reload the save
- Return to the boss fight
- The issue should be fixed
We know you've tried some steps already, these are different ones